There is an urgent need to develop a totally electric car as one of decisive factors in preventing air pollution due to motorization. With the understanding that conservation of the natural environment is a big issue in the 21st century, the inventor of the present invention started the development in 1980s and is now yielding results.
As shown in FIG. 1, an electric car is driven by using only a driving force of an electric motor 101. When a secondary battery, an engine generator, or a fuel battery is used as a power source for the electric motor 101, the electric car is respectively referred to as an electric car A in the narrow sense, a series hybrid car B, or a fuel battery car C. The reference numerals 102, 103, 104, 201, 202, 301, and 302 respectively denote a wheel, a controller, a secondary battery, an engine, a generator, a hydrogen feeding source, and a fuel battery.
As mentioned above, since the electric car is driven by using only a driving force of a rotary electric motor, it is defined as a car which uses a secondary battery, a fuel battery, a generator using an internal-combustion engine, a solar battery, or the like, or a combination of at least two of them, as a power source for the electric motor. Although the electric car uses only a secondary battery in the following description, those skilled in the art will appreciate that the present invention is applicable to a car which uses a fuel battery, a generator using an internal-combustion engine, or a solar battery as a power source.
In order to improve the safety and the ease of use of a car in driving, an electronic system essential for the safety of the car has been increasingly equipped with redundant components such as sensors and computing elements.
In a disclosed example, position sensors of an operating member which can be operated by a driver, sensors for detecting the number of revolutions, or the like are redundantly provided. A signal from a measuring device having such a redundant structure is fed to two processors, each controlling a driving output of a car in accordance with substantially the same computer program as that of the other. Output signals from the two processors act on a common variable which affects an output of a driving unit.
However, if this type of system is made fully redundant, it becomes very complicated, resulting in an increased cost and an increased frequency of failures.
As is well known, a present car is equipped with a plurality of electronic control units, in particular, including a speed control unit and a steering control unit. Each of these control units acts on another variable of a driving unit of the car.
In the present car, these control units are mutually connected to each other by an electronic connecting system and mutually exchange data and information therethrough.
Although a speed control of the electric car is performed by feeding an electrical signal from an accelerator pedal to a control device for controlling an electric current to be applied to its electric motor, when a plurality of electric motors are used to drive the car and also when an acceleration, a deceleration, and a turning angle of the car are controlled, an additional central control device for controlling the overall car is required. In such control devices, the central control device and each of the control devices fixed to the corresponding electric motors have been connected by a corresponding signal line so as to perform a control.